2. Alloy hardening and general structure-properties relationships

The development of a metal alloy can meet a variety of needs, including the achievement of specific physical properties: low dilatability (e.g. Fe-Ni alloys of the invar type), good conductivity (connector technology), low AC losses (Fe-Si alloy laminations for transformers), good magnetic properties (permanent magnets) etc.

The technical and economic optimization (performance, weight reduction, cost) of a large number of mechanical parts justifies an improvement in the resistance of the material used to cyclic stresses, i.e. mechanical strength for a given geometry and surface finish. Heat treatment of alloys is therefore often aimed at improving yield strength without too much loss of ductility.

To harden an alloy, you can either work-harden it or optimize its structure.

Hardening is generally used for parts whose...